Conventionally, there is a well-known a press molder for draw molding, comprising a die, a punch and a cushion ring, which pinches a work piece between the die and the cushion ring and presses the work piece on the punch disposed oppositely to the die so as to perform molding, as disclosed in the Japanese Patent Laid Open Gazette 2002-86219, for example.
As shown in FIGS. 30 and 31, such a press molder comprises a die 102 which is an upper mold, a punch 103 disposed oppositely to the die 102, a lower mold 104 constructed integrally with the punch 103, and a cushion ring 105 annularly disposed around the punch 103.
Such a press molder may comprise a plurality of cushion rings. For example, a press molder shown in FIG. 32 comprises a first cushion ring 105 and a second cushion ring 106 disposed inside the first cushion ring 105.
At the time of molding by moving the die 2 downward, a work piece W interposed between the die 102 and the punch 103 is pinched between a crease-suppression surface 102a of the die 102 and a crease-suppression surface 105a of the cushion ring 105 (in FIG. 32, a crease-suppression surface 105a of the first cushion ring 105 and a crease-suppression surface 106a of the second cushion ring 106) so as to prevent any crease or crack from being generated in the work piece W after the molding.
For preventing the bending at the time of draw molding, it is conceivable to provide a drawing mold with reinforcing structures, such as ribs. Conventionally, there is a well-known cast, such as a drawing mold, formed integrally with ribs, as disclosed in the Japanese Patent Laid Open Gazette Hei. 7-51796, for example.